Harpers are the musicians, singers, archivists, teachers, storytellers, artists and advisers of pern. They ensure all pernese are brought up with a basic education and knowledge their history and duty. They play all kinds of Music and write their own ballads, sonets and stories etc. They also record and keep all of the records on Pern, they can be artists as well as this is in a way a form of record keeping. They would be very good speakers and negotiators, if someone needed a representative it would be a harper. They also learn how to operate and send drum messages using the drum towers of Pern's holds, weyrs and halls.
Although harpers have to have a fairly good voice or ability to play an instrument there are many reasons why someone may make a good harper, many have nothing to do with music as all, these skills would be taught.
Percussion, a variety of pipes/flutes (while the skill to make them lasted), hammer dulcimer, guitar, violin, but no double basses, some brass, more bugle than trombone, trumpet, harp, usually the smaller lap harp but occasionally a full concert harp - much prized - or the smaller floor harp.
They would have instruments that were easy to make and carry! So if it is too complicated or the materials unavailable on Pern they wouldn't have it.